Brain mechanisms associated with depressive relapse and associated cognitive impairment following acute tryptophan depletion

BACKGROUND

Acute tryptophan depletion lowers brain serotonin synthesis and results in a transient, but striking, clinical relapse in recovered depressed patients.

AIMS

To identify brain regions which change their activity as an acute depressive relapse evolves and to determine how pathological mood might modulate neural activity during a cognitive task.

METHOD

We used H2(15)O positron-emission tomography (PET) to study eight recovered depressed men after tryptophan depletion and after a control procedure. During both PET scan sessions, subjects performed a paced verbal fluency task which alternated with a control verbal repetition task.

RESULTS

Increasing levels of depression after tryptophan depletion were associated with diminished neural activity in the ventral anterior cingulate, orbitofrontal cortex and caudate nucleus regions. In addition, depressive relapse attenuated cognitive task-related activation in the anterior cingulate cortex.

CONCLUSIONS

Our data indicate that changes in neural activity in distinct brain regions mediate the clinical phenomena of depression and depression-related cognitive impairment following acute tryptophan depletion. These changes could be associated with the widespread distribution of serotonin neurons in brain pathways associated with the expression of affect and cognitive performance.

Allelic variation of the 5-HT2C receptor (HTR2C) in bulimia nervosa and binge eating disorder

The 5-HT2C (serotonin-2C, HTR2C) receptor is implicated in the pathophysiology of eating disorders. There is a common polymorphism of the human 5-HT2C receptor at codon 23 (cys23ser) which has been reported to be a risk factor for certain psychiatric disorders and a predictor of their pharmacotherapeutic response. We examined whether this variant was associated with the eating disorder bulimia nervosa or binge eating disorder in a well-characterized community sample of 163 women, aged 16-35 years. Genotype and allele frequencies were entirely unaltered in both groups, compared to screened healthy controls from the same population. We conclude that allelic variation does not account for the involvement of the 5-HT2C receptor in these eating disorders.

c-Rel is crucial for lymphocyte proliferation but dispensable for T cell effector function

The TCR signals are essential for T cell activation and proliferation, primarily through the induction of cytokine and cytokine receptors. Several transcription factor families, including NF-kappaB/Rel, have been implicated in the regulation of cytokine gene expression in T cells in response to antigen, cytokine and mitogenic stimulation. In this study, we show that the mice with a null mutation in the lymphoid-specific c-Rel gene have normal development of lymphoid tissues and T cell compartment. However, T cells derived from the c-Rel knockout mice have several functional abnormalities. The c-Rel-deficient T lymphocytes fail to respond to activation and proliferation signals mediated by the TCR and mitogens in vitro. This is attributed to an impaired production of cytokines IL-2, IL-3 and granulocyte macrophage colony stimulating factor. In addition, the induction of IL-2R alpha chain is impaired in the c-Rel(-/-) T cells. The poor expression of cytokines and IL-2R alpha chain correlates with a reduced nuclear translocation of NF-kappaB components in c-Rel(-/-) T cells. Since activation is prerequisite for differentiation into effector cells, c-Rel(-/-) T cells failed to differentiate into cytotoxic T cells or Th cells without rescuing cytokines. However, upon supplement with exogenous IL-2, the c-Rel(-/-) cytotoxic T lymphocytes are able to execute cytotoxicity and the c-Rel(-/-) Th cells are capable of providing help to normal B cells. These data suggest that c-Rel is important for inducible cytokine and cytokine receptor expression, and a key regulator of early activation and proliferation in T cells.

Regulators of G protein signaling exhibit distinct patterns of gene expression and target G protein specificity in human lymphocytes

The newly recognized regulators of G protein signaling (RGS) attenuate heterotrimeric G protein signaling pathways. We have cloned an IL-2-induced gene from human T cells, cytokine-responsive gene 1, which encodes a member of the RGS family, RGS16. The RGS16 protein binds Gialpha and Gqalpha proteins present in T cells, and inhibits Gi- and Gq-mediated signaling pathways. By comparison, the mitogen-induced RGS2 inhibits Gq but not Gi signaling. Moreover, the two RGS genes exhibit marked differences in expression patterns. The IL-2-induced expression of the RGS16 gene in T cells is suppressed by elevated cAMP, whereas the RGS2 gene shows a reciprocal pattern of regulation by these stimuli. Because the mitogen and cytokine receptors that trigger expression of RGS2 and RGS16 in T cells do not activate heterotrimeric G proteins, these RGS proteins and the G proteins that they regulate may play a heretofore unrecognized role in T cell functional responses to Ag and cytokine activation.

Symptomatic relapse in bulimia nervosa following acute tryptophan depletion

BACKGROUND

Preclinical and clinical studies suggest that lowered brain serotonin neurotransmission may contribute to the pathophysiology of bulimia nervosa (BN). The aim of our study was to test this hypothesis by examining the psychological effects of a dietary-induced impairment in serotonin activity in subjects known to be at risk for manifestation of the clinical syndrome of BN.

METHODS

An 85.8 g amino acid mixture lacking the serotonin precursor tryptophan and a balanced mixture were administered to 10 clinically recovered, medication-free female subjects with a history of BN in a double-blind, crossover design. Twelve healthy female subjects with no history of psychiatric disorder were studied as a comparison group. Observer and self-rated measures of mood and eating disorder cognitions were made for the 7 hours following administration of each amino acid mixture.

RESULTS

Compared with healthy controls, subjects with a history of BN had significant lowering of mood, increases in ratings of body image concern, and subjective loss of control of eating following the tryptophan-free mixture.

CONCLUSIONS

Our results suggest that diminished serotonin activity may trigger some of the cognitive and mood disturbances associated with BN. Our findings support suggestions that chronic depletion of plasma tryptophan may be one of the mechanisms whereby persistent dieting can lead to the development of eating disorders in vulnerable individuals.

Transduction of human CD34+ cells that mediate long-term engraftment of NOD/SCID mice by HIV vectors

Efficient gene transfer into human hematopoietic stem cells (HSCs) is an important goal in the study of the hematopoietic system as well as for gene therapy of hematopoietic disorders. A lentiviral vector based on the human immunodeficiency virus (HIV) was able to transduce human CD34+ cells capable of stable, long-term reconstitution of nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice. High-efficiency transduction occurred in the absence of cytokine stimulation and resulted in transgene expression in multiple lineages of human hematopoietic cells for up to 22 weeks after transplantation.

Intrathecal morphine delivered via subcutaneous pump for intractable pain in pancreatic cancer

BACKGROUND

Pain secondary to unresectable pancreatic cancer is frequently severe and extremely difficult to control with traditional methods of analgesia. This retrospective study reports the analgesic effects of intrathecal morphine sulfate by implanted infusion pumps in nine patients with unresectable adenocarcinoma of the pancreas.

METHODS

Nine patients were implanted over a 2-year period. Preoperative morphine i.v. equivalents were a mean of 81.51 mg/day, with a range of 20-140 mg/day. Patients were hospitalized for a trial dose of 1-2 mg of intrathecal Duramorph, 1 mg/ml, via lumbar puncture to assess whether adequate pain relief could be achieved and whether there would be drug-related side effects.

RESULTS

All patients who received a trial dose experienced excellent pain relief, and subsequently underwent implantation of a lumbar subarachnoid catheter and infusion pump during the same hospitalization. The mean number of days from diagnosis to pump implant was 119, with a range of 3-587 days. The mean maximum daily dose was 21.28 mg, with a range of 3-73.10 mg. No patient experienced respiratory depression or excess sedation which prevented achievement of pain control. Minor supplemental narcotic use was documented in three of the nine patients. Assessment of pain control was made by the level of activity and the analog pain scale, with 0 being no pain and 10 being the worst pain imaginable. All of the patients experienced good to excellent relief of pain. The mean duration of intrathecal morphine sulfate use until death was 137.3 days, with a range of 52-354 days.

CONCLUSIONS

This series of nine patients indicates that long-term administration of intrathecal morphine via implanted infusion pump in patients with pancreatic cancer is both efficacious and safe. All patients and their families reported an improved quality of life with an increased level of activity.

Neutrophils deficient in PU.1 do not terminally differentiate or become functionally competent

PU.1 is an ets family transcription factor that is expressed specifically in hematopoietic lineages. Through gene disruption studies in mice we have previously shown that the expression of PU.1 is not essential for early myeloid lineage or neutrophil commitment, but is essential for monocyte/macrophage development. We have also shown that PU.1-null (deficient) neutrophils have neutrophil morphology and express neutrophil-specific markers such as Gr-1 and chloroacetate esterase both in vivo and in vitro. We now demonstrate that although PU.1-null mice develop neutrophils, these cells fail to terminally differentiate as shown by the absence of messages for neutrophil secondary granule components and the absence or deficiency of cellular responses to stimuli that normally invoke neutrophil function. Specifically, PU.1-deficient neutrophils fail to respond to selected chemokines, do not generate superoxide ions, and are ineffective at bacterial uptake and killing. The failure to produce superoxide could, in part, be explained by the absence of the gp91 subunit of nicotinamide adenine dinucleotide phosphate oxidase, as shown by our inability to detect messages for the gp91(phox) gene. Incomplete maturation of PU.1-deficient neutrophils is cell autonomous and persists in cultured PU.1-deficient cells. Our results indicate that PU.1 is not necessary for neutrophil lineage commitment but is essential for normal development, maturation, and function of neutrophils.

Angiographic follow-up in 37 patients after radiosurgery for cerebral arteriovenous malformations as part of a multimodality treatment approach

Modified Linac radiosurgery was utilized at our institution between 1990 and 1995 in 54 patients with cerebral arteriovenous malformations (AVMs) as part of a multimodality therapeutic approach. Most patients also underwent surgery and embolization of the AVMs prior to radiosurgery. The goal of the adjunctive radiosurgical treatment was the complete angiographic obliteration of the deep residual AVM after subtotal embolization and resection. Radiosurgery was used as the primary treatment of some small deep AVMs which were judged to have a high risk of morbidity if approached surgically. Of the 54 patients, 37 have had follow-up angiograms available for review. The median time interval between radiosurgery and the most recent angiogram was 22 months (range 5-66 months). This is a retrospective report on the angiographic follow-up available on this selected group of patients with difficult AVMs. All angiograms were evaluated for the presence of residual AVM. If any residual AVM was present, a decrease in size of more than 50% was noted as significant. The hospital and office charts of all patients were reviewed and the patients and families were contacted for up-to-date clinical follow-up. Prior to treatment, 11 patients had Spetzler-Martin grade 5 AVMs, 12 patients had grade 4 AVMs, and 14 patients had grade 3 AVMs. There were no grade 1 or 2 AVMs treated with radiosurgery. Of these 37 patients, 13 (35%) were completely obliterated on follow-up angiography. Three of the 11 (27%) grade 5 AVMs were completely obliterated. Seven of the 12 (58%) grade 4 AVMs were obliterated. Three of the 14 (21%) grade 3 AVMs have documented radiosurgical obliteration, however 8 others have had a significant decrease in size on the first posttreatment angiogram (median follow-up 14 months) and have further angiographic follow-up pending. There were 5 hemorrhages after radiosurgery, 1 was fatal and 1 resulted in permanent morbidity. Six patients have been reembolized since radiosurgery and 2 of those had their AVMs surgically resected thereafter. Only 1 patient of 6 (17%) in this series who was treated with radiosurgery alone has had documented AVM obliteration. None of 3 treated with embolization alone prior to radiosurgery have had complete obliteration. Three of the 5 patients (60%) who had only surgery prior to radiosurgery had their AVMs completely obliterated. Of the 23 patients who had all three treatments (embolization, surgery, and radiosurgery), 10 (43%) had complete obliteration of their AVMs. One patient (2%) developed moderate permanent neurological disability as a result of radiosurgery-induced necrosis. This patient did have complete obliteration of her AVM. These data support the use of radiosurgery for treatment of cerebral AVMs as part of a multimodality approach if the surgical risk of any residual AVM after embolization and microsurgical resection is deemed excessive. The adjunctive use of radiosurgery in this series resulted in the safe complete obliteration of many very difficult grade 4 and 5 AVMs. These data do not support the use of radiosurgery as the primary treatment of surgically resectable AVMs since there is a risk of interval hemorrhage and the obliteration rate is far inferior to that of microsurgical resection.

Distal posterior cerebral artery revascularization in multimodality management of complex peripheral posterior cerebral artery aneurysms: technical case report

OBJECTIVES AND IMPORTANCE: Although controversial, revascularization of the distal posterior cerebral artery (PCA) may become necessary in treating complex PCA aneurysms before proximal parent vessel sacrifice. The revascularization of the distal PCA territories of two patients with peripheral PCA aneurysms is presented.

CLINICAL PRESENTATIONS

One patient had an aneurysm of the P2-P3 segment and failed a selective P2 balloon occlusion test by developing homonymous hemianopia before planned parent vessel sacrifice. The other patient with a giant P2 segment aneurysm presented with visual field deficits.

TECHNIQUE

The distal segment of PCA was revascularized before the aneurysms were trapped by surgical clipping or coil occlusion of the distal P2 segment, proximal to the aneurysms. In both cases, the occipital artery was used as the "donor" vessel. Temporary occlusion times were 22 and 20 minutes, respectively. Both grafts were patent on postoperative angiography, and both patients had full visual fields at the time of their follow-up examinations.

CONCLUSION

De novo distal P2 sacrifice, advocated for treating peripheral PCA aneurysms, leads to visual field deficits in some patients. Revascularization of the distal segment of the PCA, less technically demanding than bypass to other PCA segments, preserves blood flow, thus sparing vision in this subset of patients.

Antigen-specific cytolysis by neutrophils and NK cells expressing chimeric immune receptors bearing zeta or gamma signaling domains

TCR- and IgG-binding Fc receptors (Fc gamma R) mediate a variety of critical biologic activities including cytolysis via the structurally related zeta- and gamma-chains. In previous studies, we have described chimeric immune receptors (CIR) in which the ligand-binding domain of a heterologous receptor or Ab is fused directly to the cytoplasmic domain of the TCR zeta-chain. Such zeta-CIRs efficiently trigger cytotoxic function of both T and NK cells in a target-specific manner. In this report, we compared the ability of both zeta- and gamma-CIRs to activate the cytolytic function of two distinct classes of Fc gamma R-bearing effectors, NK cells and neutrophils. Mature neutrophils expressing zeta- and gamma-CIR were generated in vivo from murine hemopoietic stem cells following transplantation of syngeneic mice with retrovirally transduced bone marrow or in vitro from transduced human CD34+ progenitors following differentiation. Both zeta- and gamma-based CIRs were capable of activating target-specific cytolysis by both NK cells and neutrophils, although the zeta-CIR was consistently more efficient. The experimental approach described is a powerful one with which to study the role of nonlymphoid effector cells in the host immune system and permits the rational design of immunotherapeutic strategies that rely on harnessing multiple immune cell functions via CIR-modified hemopoietic stem cells or progenitors.

Myeloid development is selectively disrupted in PU.1 null mice

The ets family transcription factor PU.1 is expressed in monocytes/macrophages, neutrophils, mast cells, B cells, and early erythroblasts, but not in T cells. We have recently shown that PU.1 gene disruption results in mice with no detectable monocytes/macrophages and B cells but T-cell development is retained. Although neutrophil development occurred in these mice, it was delayed and markedly reduced. We now proceed to demonstrate that PU. 1 null hematopoietic cells fail to proliferate or form colonies in response to macrophage colony-stimulating factor (M-CSF), granulocyte CSF (G-CSF), and granulocyte/macrophage CSF (GM-CSF). In contrast, PU.1 null cells did proliferate and form colonies in response to interleukin-3 (IL-3), although the response was reduced as compared with control littermates. Compared with control cells, PU.1 null cells had minimal expression of G- and GM-CSF receptors and no detectable M-CSF receptors. The size of individual myeloid colonies produced from PU.1 null primitive and committed myeloid progenitors in the presence of IL-3, IL-6, and stem cell factor (SCF) were reduced compared with controls. Under these conditions, PU.1 null progenitors produced neutrophils but not monocytes/macrophages. These observations suggest that PU.1 gene disruption induces additional cell-autonomous effects that are independent of the alterations in myeloid growth factor receptor expression. Our results demonstrate that PU.1 gene disruption affects a number of developmentally regulated hematopoietic processes that can, at least in part, explain the changes in myeloid development and reduction in myeloid and neutrophil expansion observed in PU.1 null mice.

A case-control study of verocytotoxigenic Escherichia coli infection in cats with diarrhea

The objectives of this study were to determine the prevalence of enteric verocytotoxigenic E. coli (VTEC) infection in a population of cats in Ontario, and to determine whether an association exists between the presence of VTEC and feline diarrhea. Fecal samples from 179 cats, representing 113 cats with diarrhea and 66 cats with normal feces, were cultured for E. coli. The fecal cultures were screened for verocytotoxin activity with a Vero cell assay. Confirmation of the presence of verocytotoxin (VT) genes was done with polymerase chain reaction (PCR) amplification; the frequency of occurrence of the genes for generic VT, VT1, and VT2 was determined. VTEC-positive samples were defined as those that demonstrated cytotoxicity on the Vero cell assay and yielded E. coli possessing one or more of the VT genes. All VTEC-positive isolates were serotyped. The overall prevalence of enteric VTEC infection in the cats was 12.3% (22/179). Statistical analysis of the case-control data showed no significant association between VTEC infection and diarrheal illness. The majority of the cats with VT-positive E. coli were positive for the presence of the generic VT, rather than for VT1 or VT2; it is therefore possible that a novel verocytotoxin gene may exist in E. coli isolated from cats. Eight VTEC strains were identified by serotyping; 4 of these serotypes have previously been isolated from humans, and 2 from cattle, suggesting that cats may be capable of acting as reservoirs for human and bovine VTEC serotypes.

Oxidative denitrification of the antitumour drug hydroxyguanidine

The oxidative denitrification of the antitumour agent hydroxyguanidine (HOG) has been investigated by radiolysis methods and EPR spectroscopy. The azide radical (N3.), a model one-electron oxidant, reacts with HOG with the rate constant 5.1 x 10(9) dm3 mol(-1) s(-1) to yield the guanidino carbon-centred radical (HOG.) which rapidly eliminates nitric oxide (k = 3.1 x 10[3] s[-1]) with the concomitant formation of urea. The HOG. undergoes conjugation with molecular oxygen to form a peroxyl radical (HOGOO.) with a rate constant 8.8 x 10(8) dm3 mol(-1) s(-1). The HOGOO. radical also eliminates nitric oxide but may act as a precursor to the peroxynitrite (ONOO-) ion. The oxidation of HOG by the dibromide radical (Br2.-) was found to release nitric oxide with a yield of 95% relative to Br2.- as determined from the combined yields of inorganic nitrite, nitrate and a HOG/nitric oxide-adduct. This study provides a possible mechanistic basis for the oxidative denitrification of HOG which may contribute to the observed toxicity of the drug both in vitro and in vivo and for the oxidation of nonphysiological hydroxyguanidines to NO. via nitric oxide synthase-independent pathways.

Rational interleukin-2 therapy

The administration of cytokines that augment the function of the immune system can be accomplished safely and without toxicity, provided a rational approach is used. Such a therapeutic method should be based upon the principles of pharmacology and the structure-activity relationships of the cytokine-receptor interaction. Thus, the therapeutic index should be determined, and the goal should be to augment the function of the immune system in a variety of clinical situations, not necessarily focused on eradicating a particular disease process such as metastatic cancer that may or may not be influenced by the immune system.

Esophageal candidiasis as a complication of inhaled corticosteroids

BACKGROUND

Oropharyngeal candidiasis is a well-described side effect of inhaled corticosteroids. Nevertheless, few cases of esophageal candidiasis have been reported.

OBJECTIVE

To present a patient with esophageal candidiasis associated with inhaled corticosteroids.

METHODS

Case report.

RESULTS

Our patient is a 70-year-old white woman with a 20-year history of intrinsic asthma, well controlled on triamcinolone acetonide 400 micrograms, ipratropium bromide 36 micrograms, and pirbuterol acetate 400 micrograms, each inhaled four times daily. She reported no oral steroid use for > 4 years and that she always rinsed her mouth following triamcinolone acetonide inhalation. The patient had gastritis with peptic ulcer disease in the past and developed worsening dyspeptic pain and heartburn. Following discontinuation of cimetidine and initiation of ranitidine without improvement, esophagogastroduodenoscopy was performed. Several small white patches in the mid and distal esophagus could not be removed with pressure. A biopsy confirmed the diagnosis of candidal esophagitis. Following a 4-week course of fluconazole, the patient was clinically improved and follow-up esophagogastroduodenoscopy was normal. There was no evidence of underlying cellular immunosuppression, malignancy, or diabetes mellitus and no history of recent antibiotic usage. Delayed skin tests revealed 5 x 5 mm induration to dermatophytin. Delayed hypersensitivity to Candida and mumps tests was absent. There was strong in vitro lymphocyte transformation and a positive immediate skin test response to Candida. ELISA for human immunodeficiency virus was negative. T and B cell counts were normal with CD4 = 630/mm3, CD8 = 520/mm3, and absolute B cell = 120/mm3. It is possible that this patient's immediate hypersensitivity response to Candida suppressed her delayed response. Candidal esophagitis is a rare, yet important, complication of inhaled corticosteroid use.

CONCLUSION

Immunocompetent patients on inhaled corticosteroids with medically unresponsive symptoms of esophagitis should be investigated for esophageal candidiasis.

Relapse of depression after rapid depletion of tryptophan

BACKGROUND

Major depression is a common disorder but the pathophysiology is poorly understood. Current hypotheses implicate deficient function of brain serotonin pathways because drugs that selectively increase brain serotonin activity are effective antidepressants. However, there is no direct evidence that lowered serotonin function causes major depression. We aimed to assess whether lowering of brain serotonin activity by depletion of its amino acid precursor, tryptophan, could provoke a short-term relapse of clinically significant symptoms in women vulnerable to major depressive disorder.

METHODS

We studied 15 women who had suffered recurrent episodes of major depression but had recovered and were no longer on drug treatment. Patients received two amino acid mixtures in a double-blind crossover design. One of the mixtures was nutritionally balanced and contained tryptophan and the other was identical except it contained no tryptophan. Participants were scored on the Hamilton rating scale for depression (HAMD) before and 7 h after drinking each mixture. They also completed hourly self-rated measures of mood during this period. Blood samples were also taken at baseline and 7 h for measurement of plasma tryptophan.

FINDINGS

The tryptophan-free mixture produced a 75% reduction in plasma tryptophan concentration. After drinking the tryptophan-free mixture, ten of the 15 women experienced temporary but clinically significant depressive symptoms. The mean difference in total HAMD scores (7 h minus baseline) were significantly higher after the tryptophan-free mixture than after the nutritionally balanced mixture (7.3 vs 0.15 [95% CI 4.5-9.9]; p < 0.001). No changes in mood were seen after taking the nutritionally balanced mixture.

INTERPRETATION

We conclude that rapid lowering of brain serotonin function can precipitate clinical depressive symptoms in well, untreated individuals who are vulnerable to major depressive disorder. The findings support a key role for deficient serotonin function in the aetiology of depression.

Multiple mechanisms of N-phosphonacetyl-L-aspartate resistance in human cell lines: carbamyl-P synthetase/aspartate transcarbamylase/dihydro-orotase gene amplification is frequent only when chromosome 2 is rearranged

Rodent cells resistant to N-phosphonacetyl-L-aspartate (PALA) invariably contain amplified carbamyl-P synthetase/aspartate transcarbamylase/dihydro-orotase (CAD) genes, usually in widely spaced tandem arrays present as extensions of the same chromosome arm that carries a single copy of CAD in normal cells. In contrast, amplification of CAD is very infrequent in several human tumor cell lines. Cell lines with minimal chromosomal rearrangement and with unrearranged copies of chromosome 2 rarely develop intrachromosomal amplifications of CAD. These cells frequently become resistant to PALA through a mechanism that increases the aspartate transcarbamylase activity with no increase in CAD copy number, or they obtain one extra copy of CAD by forming an isochromosome 2p or by retaining an extra copy of chromosome 2. In cells with multiple chromosomal aberrations and rearranged copies of chromosome 2, amplification of CAD as tandem arrays from rearranged chromosomes is the most frequent mechanism of PALA resistance. All of these different mechanisms of PALA resistance are blocked in normal human fibroblasts.